Master the board step 3

Master the Boards: USMLE Step 3
Growth, Nutrition, and Development
Exam Tips on Pediatric Growth
Birth weight is normal
in patients with either
genetic short stature or
constitutional delay of
growth. Patients with either
condition have normal
growth velocity, which is
below and parallel to the
normal growth curve.
··
Birth weight normally doubles by 6 months and triples by 1 year.
··
Height percentile at 2 years of age normally correlates with final adult height
percentile.
··
Best indicator for acute malnutrition is weight/height < 5th percentile.
··
Best indicator for under- and overweight is BMI.
··
Skeletal maturity is related to sexual maturity (less related to chronologic age).
··
The most common cause of failure to thrive in all age groups is psychosocial
deprivation.
··
All cases of underfeeding must be reported to child protective services (CPS).
··
You must work up any child who has crossed 2 major growth percentiles.
Description of
Growth Pattern Differential Diagnosis Workup
↓ weight gain
more than
↓ length/height
Normal weight gain
↓ length/height
↓ weight gain
equals
↓ length/height
• Undernutrition
• Inadequate digestion
• Malabsorption (infection,
celiac disease, cystic fibrosis,
disaccharide deficiency,
protein-losing enteropathy)
• Growth hormone or thyroid
hormone deficiency
• Excessive cortisol secretion
• Skeletal dysplasias
Systemic illness:
• Heart failure
• Inflammation (e.g.,
inflammatory bowel disease
or arthritis)
• Renal insufficiency
• Hepatic insufficiency
Genetic short stature
Constitutional delay in growth
and development
Assess caloric intake
Perform stool studies for fat
Perform sweat chloride test
Growth hormone (GH) deficiency:
• Insulin-like growth factor 1 (IGF-1) and IGF-binding
protein 3 (IGF-BP3)
Thyroid hormone:
• TSH, free T4, free T3
Cushings:
• 24-hour urinary cortisol or free cortisol
Bone age (x-ray of hand and wrist):
• Skeletal dysplasia: no delay in bone age and
disproportionate bone length on exam
Inflammatory markers:
• CRP, ESR, CBC with diff
Organ dysfunction:
• LFT, creatinine, BUN
• Electrolytes
Bone age:
• Genetic short stature: The bone age is close to the
chronological age; puberty occurs at the normal time.
• Constitutional delay of growth: The bone age is delayed,
and puberty occurs later than in most children.
374